Traveling-wave tube with a vacuumtight ceramic window

ABSTRACT

A traveling-wave tube is provided with a waveguide having a vacuumtight ceramic window therein disposed at the line of separation of a pair of separate portions of the waveguide. The ceramic window includes beveled edges which form solder limiting means along the inner surface of the waveguide during bonding of the window therein. A metal ring or band is tightly secured within a recess about the waveguide adjacent the ceramic window and includes at least one circumferentially disposed slot therein situated at the point of coupling of the tubular waveguide portions.

United States Patent Gross et al.

[54] TRAVELING-WAVE TUBE WITH A VACUUMTIGHT CERAMIC WINDOW {72] Inventors: Franz Gross; Paul Kahl, both of Munich; Peter Mammach, Oberschleissheim, all of Germany [73] Assignec: Siemens Aktiengesellschaft, Berlin and Munich, Germany [22] Filed: June 11, 1970 [211 App]. No.: 45,510

[30] Foreign Application Priority Data June 23,1969 Germany ..P 19 31 712.5

[52] US. Cl ..333/98 P, 315/39 [51] ..H0lp 1/08 [58] FieldofSearch ..333/98,98 P;3l5/39,5

[56] References Cited UNITED STATES PATENTS 3,156,882 ll/ 1 9g4 aug ..333/98 1 Feb. 29, 1972 3,l56,88l 11/1964 Bondley ..333/98 3,058,074 l0/l962 Kane ..333/98 2,931,942 4/l960 Stmad ..315/39 Primary Examiner-Mennan Karl Saalbach Assistant Examiner-Marvin Nussbaum Altomeyl'lill, Sherman, Meroni, Gross & Simpson [5 7] ABSTRACT A traveling-wave tube is provided with a waveguide having a vacuumtight ceramic window therein disposed at the line of separation of a pair of separate portions of the waveguide. The ceramic window includes beveled edges which form solder limiting means along the inner surface of the waveguide during bonding of the window therein. A metal ring or band is tightly secured within a recess about the waveguide adjacent the ceramic window and includes at least one circumferentially disposed slot therein situated at the point of coupling of the tubular waveguide portions,

6 Claims, 2 Drawing Figures PATENIEUFEBZQIENZ 3 4 4 5 INVENTORS F7002 gross pau/ l afi/ e/er MOM/W004 P WW ms TRAVELING-WAVE TUBE WITH A VACUUMTIGll-IT CERAMIC WINDOW BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a disc-seal tube, and more particularly to a travelling-wave tube having at least one coupling tubular wave guide which includes a vacuumtight window.

2. Description of the Prior Art The coupling in and coupling out of energy with disc-seal tubes over coaxial lines or coupling tubular wave guides generally requires the utilization of dielectric windows which are arranged in the run of the coupling lines since such tubes must be evacuated to a great extent. With most disc-seal tubes, particularly travelling-wave tubes, the material of the tubular waveguide may not be magnetic in the range of the vacuum window, since the window is almost always in the range of the focusing field which is necessary for proper functioning of the tube, and disturbing reactions to the course of the electron beam are to be prevented. Accordingly there is a difficult technical problem in connecting a massive ceramic window within the waveguide in a vacuumtight manner in which the ceramic window comprises primarily aluminum oxide, particularly purest aluminum sapphire or beryllium oxide, and the tubular waveguide comprises a nonmagnetic material having good heat conductivity, as for instance vacuum copper, Curotherm or silver bronze. If a ceramic window is soldered into such a tubular waveguide, for instance a copper tubular waveguide, looseness and cracks appear, particularly occurring during necessary followup solderings and when the tube is baked out due to the great heat expansion differences of copper and ceramic.

SUMMARY OF THE INVENTION The object of the present invention is to provide a broadband, vacuumtight coupling in and coupling out window with good heat dissipation, a broad sealing surface, great mechanical stability and good reproducability of the matching magnitudes, having the danger of poor fit and cracks eliminated to a large degree.

In achieving the foregoing object, we propose that, according to this invention, in a disc-sealed tube of the aforementioned kind, the coupling tubular waveguide is surrounded about its outer surface by a tightly fitting metal ring in the area of the ceramic window, which ring has a coefficient of thermal expansion which is smaller than that of the tubular waveguide material. Metal ring is intended to include ringlike constructions such as a member having a generally oval cross section.

In a further development of the invention it is provided that the metal ring is composed of two half-rings which are soldered onto the outer surface of the coupling tubular waveguide with a separating line.

The metal ring, or such two-part band, reduces the expansion of the tubular waveguide surrounding the ceramic window in the critical range of the ceramic window during heating. Due to the plasticity of the copper, the metal-ceramic soldering is not strained so much by temperature fluctuations as previously encountered.

The coupling tubular waveguide advantageously includes an outer recess therein so that the effect of preventing an excessive expansion of the tubular waveguide is particularly utilized without impairing the mechanical stability of the apparatus since just at the point of the recess the tubular waveguides are strengthened by the ceramic windows soldered therein. With most coupling tubular waveguides consisting of copper, preferably molybdenum is chosen for the metal ring or metal half-rings as the case may be.

In a further development it is provided that the coupling tubular waveguide has a separating line which, at least partly, is filled by solder material, while the metal ring or these halfrings have at least one slot in circumferential direction disposed at the point of the separating line of the tubular waveguide. For the simple production of a good metal-ceramic soldering with limited flowing area of the solder, not only one but preferably two divided tubular waveguide followup housings of vacuum copper are employed in an arrangement according to this invention. Due to the dividing of the copper housing, the solder can be distributed in a central plane along the circumference of the metallized ceramic window. As soon as the soldering temperature is reached, the solder wettens the contact surfaces of the tubular waveguide and the metallized ceramic on the leftand right-hand sides of the separating line. By means of grinding down the edges of the ceramic block to form metallic bevels, the axial solder flow is limited, whereby the use of such bevels has the additional advantage that this way the outflow of the solder material, and thus the termination of the soldering process, can be recognized in a simple manner. The longitudinal slot which exist in the half-rings made of molybdenum thereby provides that the solder material does not flow off from the tubular waveguide solder spot to the tubular waveguide band solder spot. During the soldering process, the entire arrangement is clamped under pressure in a mounting support.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and features of the invention, its organization, construction and operation will be best understood from the following detailed description thereof taken in conjunction with the accompanying drawings, in which:

FIG. 1 is an elevational view of coupling apparatus according to the present invention, shown partially in section; and

FIG. 2 is a sectional view taken along the line II-II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 and 2, there is illustrated coupling apparatus in the form of a pair of coupling tubular waveguides 4 and 5 disposed in an end-to-end relation with the adjacent ends thereof extending over a ceramic block window 1. The ceramic window 1 has its edges ground for the formation of metallized bevels 2. The adjacent ends of the waveguides 4, 5 have a narrow separation of gap 6 therebetween which is, at least partially, filled with solder material. A pair of half-rings 7, 8,

preferably molybdenum are placed about the outer surface of the joined waveguides over the gap 6 with a solder foil, for example a gold copper foil, arranged in-between in such a way that the separation or gap 6 lies approximately in the center of a slot 9 which is formed in each of the molybdenum half-rings 7, 8. After clamping this arrangement into a mounting support which presses the molybdenum half-rings onto the outer surface of the tubular wave guides 4 and 5, the entire apparatus is heated in excess of the melting point of the solder material so that the ceramic window is soldered with the inner wall of the tubular waveguides as well as the molybdenum half-rings with the outer surface of the waveguides. Inductive metallic apertures 10 are provided at the sides of the inner wall of the tubular wave guide lying opposite each other, which apertures enlargen the transmission range to provide the window with a broadband characteristic.

This invention is not limited to the illustrated embodiment. For example, it is not necessary that the coupling window have a squared or oval shape as is illustrated in the drawing. Furthermore, neither the use of copper as a tubular waveguide material, nor the use of molybdenum as the ring or band is essential, but it is highly important that the material of the halfrings which form the band has a smaller thermal expansion coefficient than the material of the tubular waveguide.

Many changes and modifications of the invention will be apparent to those skilled in the art and it is to be understood that we wish include within the patent warranted hereon all such changes and modifications as may reasonably and properly. be included within the scope of our contribution to the art.

What we claim as our invention is:

l. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuumtight within said tubular waveguide; and a metal ring having a coetficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said metal ring comprising at least two portions separated and secured to said tubular waveguide.

2. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuumtight within said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said tubular waveguide including a pair of tubular waveguide portions spaced apart to provide a gap therebetween in the adjacent end at approximately one-half the thickness of said ceramic window, said gap being at least partially filled with a solder material.

"3. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuum tight within said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said tubular waveguide including means defining a recess in the outer surface thereof adjacent said ceramic window, and said ring disposed within said recess.

4. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuum tight within said tubular waveguide, said ceramic window including beveled edges which limit solder flow along the inner surface of said tubular waveguide during the bonding of said ceramic window to said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window.

5. Coupling apparatus according to claim 2, including means forming a slot in said metal ring in its'circumferential direction adjacent said gap.

6. Coupling apparatus according to claim 1, wherein said wave guide comprises copper and said metal ring comprises molybedenurn. 

1. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuumtight within said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said metal ring comprising at least two portions separated and secured to said tubular waveguide.
 2. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuumtight within said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said tubular waveguide including a pair of tubular waveguide portions spaced apart to provide a gap therebetween in the adjacent end at approximately one-half the thickness of said ceramic window, said gap being at least partially filled with a solder material.
 3. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuum tight within said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window, said tubular waveguide including means defining a recess in the outer surface thereof adjacent said ceramic window, and said ring disposed within said recess.
 4. Coupling apparatus for a travelling-wave tube comprising: at least one tubular coupling waveguide; a ceramic window secured vacuum tight within said tubular waveguide, said ceramic window including beveled edges which limit solder flow along the inner surface of said tubular waveguide during the bonding of said ceramic window to said tubular waveguide; and a metal ring having a coefficient of thermal expansion smaller than that of said waveguide secured and tightly fitting about said waveguide adjacent said ceramic window.
 5. Coupling apparatus according to claim 2, including means forming a slot in said metal ring in its circumferential direction adjacent said gap.
 6. Coupling apparatus according to claim 1, wherein said wave guide comprises copper and said metal ring comprises molybedenum. 